Electric heater



Dec. 22, 1925 1,566,507

T. C. RUSSELL ELECTRI C HEATER Filed June 21, 1924 Patented Dec. 22,

PATENT OFFICE.

THOMAS C. RUSSELL, OF CHICAGO, ILLINOIS.

ELECTRIC HEATER.

Application filed June 21, 1924. Serial in. 721,449.

To all whom it may concern:

Be it known that I, THOMAS C. RUssELL, a citizen of the United States, and a resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Electric Heaters, of which the following is a specification.

My invention relates to electric heaters, particularly that type used for space heating, or for conduction heating when clamped intimately against the walls of containers, machineparts, or other objects to be heated. In this type of heater one or more resistance elements .in the form of wires or ribbons are enclosed in a long flat, metallic protecting sheet of steel or other suitable metal and connected at their ends with terminal structures secured on the sheath.

The metal sheath not only protects the resistance or heat element, but should also be adapted. to quickly conduct away the heat from the element. The sheath walls should therefore be intimately compressed against the resistance element throughout its length so as to eliminate any chance for local accumulation of heat and burning out of the element. The construction of the heater should therefore be such that the sheath may be readily subjected throughout its length to pressure in order that its walls may be brought uniformly and intimately against and around the resistance element. An important object of my invention is therefore to provide simple terminal supportin structures which can be readily detachab iy applied at the ends of the sheath to support the terminals with which the ends of the resistance elements are connected, such ends being preferably in the form of ribbons intimately connected with the resistance element ends between the sheath walls and extending from the ends of the sheet to the terminals on the supporting frame.

Where the heaters are to be used for conducting heat directly to objects to be heated, it is very important that the base thereof be clear of any obstructions so that the heater can be pressed throughout its extent firmly and intimately against the surface of the object to be heated so that the sheath walls will rapidly conduct the heat from the resistance element to the object. An-

other important objeot of my invention is therefore to provide terminal frames which can be rigidly secured across the ends of the sheet but entirely clear of the space or object engaging surface thereof.

Another object of the invention is to provide terminal frames adapted to receive terminals of different types, as for example, plug terminals, Fahnestock terminals, or the ordinary screw nut terminals.

Another important object of the invention is to provide a terminal frame which will protect the terminals from excessive heat and keep them relatively cool.

The above and other features of my invention are disclosed in the structure shown on the accompanying drawing, in which- Fig. 1 is a plan view of a heater,

Fig. 2 is a side elevational view with one end in median vertical section,

Fig. 3 is an end View,

Fig. 4 is an under side view of one end of the heater with the terminal frames removed, and

Figs. 5 and 6 are side views showing modified forms of terminals.

The long flat sheath S is formed of suit able sheet metal. preferably steel, the side sections A and B being turned over into parallelism with the top C. Extending longitudinally through the sheath are one or more resistance or heat elements 10, the elements shown being in the form of resistance wire bent in zigzag fashion. The elements are insulated from each other and from the sheathing by a wrapping of insulating material such as mica 11 which preferably extends a short distance beyond the ends of the sheath. At the ends the resistance wires are secured to the terminal ribbons 12 having the holes 13 at their outer end for enabling them to be readily connected with terminals. The ribbons extend a short distance into the sheath to be firm- 1y clamped in position by the sheath walls. Before the sheathing sides A and B are turned down a pressure plate D is applied for sealing the gap between the side edges and for assisting the sides in securely clam ing the insulation and resistance wires. e sheath with the insulation, resistance wires, and terminal ribbons is then subjected in a suitable press to heavy uniform pressure which will intimately and powerfully press the sheath sides together and as closely as possible at all points to the resistance wires so that there will be no chance for localization of heat and consequent burning of the wires. I 5

The terminal supporting frames F are of rectangular shape, each comprising the rectan la'r fiat upper wall 14- and the vertical side walls 15 and 16 which terminate in transversely curved flanges 17 and 18 respectively, these flanges accurately fitting and receiving the edges of the sheath S. The frames are applied at the ends of the sheath, and screws 19 extending through the side walls thereof serve to draw the side walls together and hold them in firm clamping engagement with the sheath edges thus to securely anchor the frames in place. Suitable terminals are supported on the top wall 14 of each frame and connected with theterminal ribbons of the resistance wires. As shown in Figs. 1, 2 and 3, a pair of plug terminals in provided, each comprising a flat blade 20 and a threaded shank 21 for extending through a hole 22 in the to wall 14,11. washer 23 being inserted to a ford good seating for the blade. The shank of each terminal below the top wall 14 receives a clamping nut 24 and a seating washer 25 therefor, suitable insulation 26 being interposed between the terminal and the washers to thoroughly insulate the terminal from the supporting frame. Each terminal receives one of the ribbons 12, such ribbons being bent around the end of the sheath with itshole 13 receiving the terminal shank, to be thenfirmly electrically connected with the terminal by being clamped between the nut 24 and washer 25. The insulation which extends beyond the sheath ends will insulate the ribbon from the sheath walls and the frames F will protect the terminal ribbons against mechanical injury. The to walls 14 of the frames are also spaced a su ficient difference above the sheath to wall to leave circulation space for air whic will keep the ribbons and the-terminals. from becoming overheated.

In assembling the sheath and frames, the terminal ribbons can first be secured to the terminals and the frames then applied and clamped to the sheath ends.

For replacement of terminals or other reasons the frames can be readily detached by withdrawing the screws 19. It will be noted strengthen the heater structure and protect the ends thereof, and as these frames are entirely within the ends of the sheath a great saving in space-is effected, particularly where a number of heaters are utilized, or mounted within enclosures or on panels.

In Fig. 5 I show the well known type of Fahnestock terminal 28, and in Fig. 6 I show L terminals 29 with terminal screws 30 and nuts 31. In each case the terminals are within the ends of the sheathing so that the entire length of the heater is no greater than the length of the sheath.

I thus produce a simple and efficient heater of the class described.

I do not desire to be limited to the exact construction and arrangement shown and described as modifications may be made which will still come within the scope of the invention.

I claim as follows:

1. In an electric heating deviceof the class said frame engaging with the side edges of said sheath, means for drawing said walls into clamping engagement with said edges to thereby clamp the frame in place, said walls being clear of the base of said sheath whereby said sheath may be applied to flat surfaces, terminals on said frame, and connections between said resistance element and said terminals.

2. In an electric heat element of the class described, the combination of a flat elongated metallic sheath, a resistance element extending through said sheath and insulated therefrom, a metallic terminal su porting frame bridging the top of said sheath at one end thereof, said frame comprising a top wall separated from the sheath by an air space and having side walls engaging with the side edges of said sheath, means for causing said side walls to clamp the edges of said sheath to thereby secure the frame in place, terminals on said frame, and means for connecting said terminals with the ends of said resistance element.

3. In an electric heat device of the class described, the combination of a flat elongated metallic sheath, a resistance element extending through said sheath and insulated therefrom, a terminal supporting frame on top of said sheath, said frame having side walls fitting and receiving the side edges of said sheath, means engaging said side walls to cause them to transversely clamp the sheath between them to thereby support the frame, terminals mounted on said frame, and means connecting said terminals with said resistance element.

4'. In an electric heat device of the class described, the combination of a flat elongated metallic sheath, .a resistance element within said sheath, a sheet metal supporting frame comprising a top Wall and side walls, means clamping said side Walls against the side edges of said sheath to support said top Wall a distance away from said sheath, terminals on said top wall, and means connecting said terminals with the ends of said resistance element.

5. In a heating device of the class described, the combination of a flat elongated metallic sheath, a resistance element Within said sheath insulated therefrom, a sheet metal frame transversely bridging and de tachahly mounted on the top side of said sheath to leave the base of the sheath free for intimate application to a surface to be heated, terminals on said frame, and means connecting the ends of said resistance element with said terminals.

6. In an electric heat element of the class described, the combination of a flat elongated metallic sheath, a resistance element Within said sheath insulated therefrom, a sheet metal supporting frame transversely bridging the top side of said sheath near the end thereof and (letachably secured to the sheath to leave the base of the sheath free for intimate application to a surface to be heated, terminals on said frame, and connections extending from said resistance element into said frame and connected with said terminals.

7. In an electric heat device of the class described, the combination of a flat rectangular metallic sheath, a resistance element within said sheath, a sheet metal frame transversely bridging and detachably secured on top of said sheath at the end thereof, terminals on said frame, and connections extending from said resistance element into said frame and secured to said terminals.

8. In an electric heat device of the class described, the combination of a flat elongated metallic sheath, a resistance element extending through said sheath but insulated therefrom, a rectangular sheet metal supporting frame on the top side of said sheath at one end thereof, side walls for said frame receiving the side edges of said sheath, detachable means for clamping said walls intimately against the sheath edges but clear of the sheath base, terminals on said frame, and means connecting said terminals with the ends of said resistance element, said connecting means extending-from the end of said sheath into said frame.

In witness whereof, I hereunto subscribe my name this 14th day of June A. D., 1924;.

THOMAS C. RUSSELL. 

